A turbomachine comprises a low-pressure compressor and a high-pressure compressor each driven by a rotary shaft and interconnected by an intermediate casing that defines an annular flow passage for a primary air stream passing from the low-pressure compressor to the high-pressure compressor. A sealing annular end plate is carried by the intermediate casing and extends between bearings for guiding the compressor shafts. A radially inner end of the end plate has labyrinth seals co-operating with the downstream and upstream ends respectively of the low- and high-pressure compressor shafts. This end of the end plate also has radial chimneys in which tubes are mounted for pressurizing the internal enclosure, these tubes extending in radial ducts of the intermediate casing that open out into the primary air passage in order to be fed with air under pressure. This air under pressure prevents oil for lubricating the bearings that guide the compressor shafts from leaking out through the labyrinth seals.
In order to enable them to be mounted, the pressurization tubes are engaged in the radial chimneys of the annular end plate and then the end plate is fastened to the intermediate casing. The radially outer ends of the tubes are then engaged in their service position in the radial ducts of the intermediate casing. An annular collar incorporated in each tube serves to hold the tubes in this position by using an annular flange mounted around each tube and fastened by bolting to a corresponding flange on each of the radial ducts of the intermediate casing.
During this mounting operation, the sealing rings that are housed in grooves at the ends of the tubes need to be engaged in and extracted from the radial chimneys of the annular end plate several times, and that runs the risk of damaging them.
Furthermore, such mounting is possible only on turbomachines of large diameter, in which it is possible to move the tubes radially inwards in the radial chimneys of the end plate over a distance that is sufficient for the outer ends of the tubes to be well clear of the radial ducts of the intermediate casing and avoid interfering therewith while the end plate is being fastened to the intermediate casing.
In turbomachines of small diameter, the axial distance between the compressor shafts is small and the space that lies radially inside the radial chimneys of the end plate is generally occupied in part by bearing nuts carrying the labyrinth seals, thereby preventing the pressurization tubes being moved radially inwards as is required for mounting them.